Epidemiological observations revealed that individuals who regularly consumed whole grain foods had lower fasting insulin and reduced risk for mortality from cardiovascular disease, cancer, and all causes compared to those who rarely ate whole grains. These associations were independent of body weight, exercise, other dietary behaviors, and other lifestyle behaviors. Therefore, the purpose of this proposed research is to collect pilot data for future experiments to examine the effect of specific types and doses of dietary whole grain on components of insulin action and other metabolic measures related to chronic disease development. A randomized crossover design will be employed with six weeks of mixed whole grain consumption, six weeks of usual diet washout, and six weeks of mixed refined grain consumption in 12 middle-aged sedentary adults at risk for type 2 diabetes. All food will be provided and the two diets will differ only in the quality of grains. The refined grain diet will include white bread, refined grain breakfast cereal, muffins, but no whole grain foods. The whole grain diet will include whole grain bread, breakfast cereal, muffins, pasta, and other whole grain foods. The primary measure of insulin sensitivity will be rate of glucose infused to maintain euglycemia during the euglycemic hyperinsulinemic clamp procedure. More physiologic and indirect measures of insulin action will include fasting insulin and insulin response following ingestion of a liquid meal. Blood pressure, and serum samples for blood lipids, markers of lipid and tissue oxidation, and other potential markers that might explain an effect of whole grains on insulin, such as serum minerals and antioxidants, will also be collected and subsequently examined as other potential mechanisms whereby whole grain consumption might reduce the risk for chronic disease development.